There was never really any doubt that Rune Factory 3 would eventually make its way overseas, but Nintendo Power have been nice enough to confirm it couldn’t too far off. The table of contents for the July 2010 issue includes a listing for it on page 18.
No publisher is mentioned; however, there’s really no reason to assume it wouldn’t be Natsume as they’ve done such a fantastic job with the games in the past, and have a long-standing relationship with Marvelous. For those that are just getting caught up, Rune Factory 3 features an upgraded character interaction system by which the townspeople don’t act entirely independently of each other.